1. Field of the Invention
The present invention relates generally to photovoltaic devices and manufacturing methods thereof and, more particularly, to a flexible photovoltaic device having a large area and a method of manufacturing such a device.
2. Description of the Background Art
FIGS. 1A-1D illustrate a manufacture process of a flexible photovoltaic element shown in Japanese Patent Laying-Open No. 1-105581.
Referring to FIG. 1A, a flexible transparent insulator film 2 is formed on a supporting substrate 1. A photoelectric conversion film 3 is formed on transparent insulator film 2. Photoelectric conversion film 3 includes a transparent front electrode, an amorphous semiconductor film for photoelectric conversion, and a back electrode stacked in this order on the transparent insulator film 2. Output terminals 4 connected to the front and back electrodes are provided on the back electrode side.
Referring to FIG. 1B, a flexible resin layer 5 having holes corresponding to output terminals 4 is formed on photoelectric conversion film 3.
With reference to FIG. 1C, transparent insulator film 2 is separated from supporting substrate 1 in water, resulting in a flexible photovoltaic element 10 shown in FIG. 1D.
Resin layer 5 formed on a back surface of photoelectric conversion film 3 is provided to prevent flexible photovoltaic element 10 from curling. More specifically, flexible photovoltaic element 10 is in general liable to curl due to the shrinking force of transparent insulator film 2 in the absence of resin layer 5. Thus, resin layer 5 having equal shrinking force with that of transparent insulator film 2 is formed on the back surface of photoelectric conversion film 3.
Polyimide resins which are flexible and superior in heat resisting properties have conventionally been used as the material of transparent insulator film 2. Photovoltaic element 10 utilizing such polyimide resins is flexible and can also easily be attached onto a curved surface.
Photovoltaic element 10 shown in FIG. 1D cannot require a significantly large area due to restrictions on the manufacture thereof, and hence the element has in general an area of 10 cm.times.10 cm. Thus, a plurality of photovoltaic elements 10 are combined together when a photovoltaic device which supplies electric power of several watts or more is formed.
In the combination of photovoltaic elements 10, leads are soldered between output terminals 4 on photovoltaic elements 10. A common front protection film made such as of PET (Polyethylene terephthalate) is attached onto transparent insulator films 2 of electrically connected photovoltaic elements 10. In order to protect the output terminals 4 and the leads, a common back protection film made of PET is attached onto resin layer 5. This results in a flexible photovoltaic device having a large area and including plurality of photovoltaic elements 10.
In the photovoltaic device with a large area according to the above-described conventional art, resin layer 5 should be provided in order to prevent the curling of photovoltaic elements 10, and the back protection film should be attached thereon. Accordingly, the photovoltaic device according to the conventional art requires a large number of material parts or components and can hardly attain a sufficient flexibility.